Messages

1

Technical / COILS

« on: August 09, 2014, 08:43:35 pm »

HI ALL ,Has anyone built a oval type coil ,I was thinking to build a 14x6 or so eliptical mono coil for sd-gp M/L..
I have built a few coils for VLF units that work Ok ,But these PI units are new to me ..

I bought some Litz-wire from Woody for a coil ..

I thought an open-coil [no coil housing] wind-coil !!,add,shielding!!,then wrap,with fibre-glass tape &seal with resin..

ANY IDEA'S & help would be greatly appreciated..

CHEERS,,BARRY..

2

Technical / F1A4 power plug pin-out query ..

« on: June 04, 2014, 07:38:17 pm »

HI ALL ,,I guess I am posting in the correct page ?.
I was wondering if anyone could PLEASE- explain the 4x lighter wires that run from socket to board ?.

The 2x heavier pos&neg wires carry slighty less than actual battery voltage ,, I did read the service manual [D/load available from M/L] & that states that when battery voltage drops the F1A4 compensates [black-box underneath battery compartment] ?? & delivers correct operating voltage to get maximum life from the Dcells..

MAYBE the 4x lighter wires are for some accessary [thesocket is named power &accessaries??

MAYBE they are'' programming pins''? as I see no other port , but the service manual say's there is one ??

The reason I ask this is I was looking to CHANGE THE Battery set-up ..& do not want to kill the Detector..

A Schematic diagram would be Nice but I guess M/L would not be forthcoming HA,Haaar..

CHEERS ,,,,BARRY..

3

Technical / Re: DC Offset in operational amplifiers in DC coupled front ends of P.I detectors

« on: June 02, 2014, 06:25:58 pm »

HI,, WOODY ,,OK THANKS FOR THAT EXPLANATION..

CHEERS,,, BARRY..

4

Technical / Re: DC Offset in operational amplifiers in DC coupled front ends of P.I detectors

« on: June 01, 2014, 08:52:12 pm »

HI WOODY & ALL ,,Reguarding the offset mentioned above I was curious as to whether this AD797 is similar to the NE5534 chip as used in many of the VFL units such as the IDX I built -up [input preamp ]..

Just curious ,,CHEERS BARRY..

5

General Discussion / some pics of F1A4 ..

« on: June 01, 2014, 08:27:24 pm »

HI ,,,ALL In my first post I mentioned the mod I did to the std F1A4 lower stalk to make it easy to adapt commercial coils ..

I also built a little amp for enhancing the sound , Just a LM386 chip & a few caps & resistors vol pot & boost switch ,powered by a 9v batt ,Housed in an Altoids tin ..can run to speaker & or H/phones works a treat ..there maybe better chips but I had this LM386 in my bits&pieces,spares..

ON the F1A4 the std speaker is awfully quiet ,I removed it & placed an alluminium Disc [Grounded to the coil socket shielding foil-[ie] little black wire]  in place of speaker to allow for future switches -pots etc any mods I may come aross

CHEERS ,,, BARRY in SA..

6

General Discussion / HI to all members

« on: June 01, 2014, 01:17:05 pm »

HI ,,,,,to all members , I have just joined this interesting site ..

I Am a 74-Y/old tinkerer & just decided to get into metal detecting A bit late in life But What the hell ..

MY previous hobbies were Speedway racing -Dirt circuit etc etc ,,Electric Guitar & the building of effects & valve amps etc,etc..
I am a Mechanic& welder [my trade ] But now only a pensioner ..
I was always interested in M/Detecting ,But never got around to doing it ,Untill recently..

I started out by obtaining a pc board of a whites IDX ,& building that,then making a few Coils for it ,,,this wet my & perked my old Grey matter ..

I sold some of my music gear & bought a whites GMT 3-[so far only used in my back-yard ,..
But after reading some Metal detector forums Found-out that one really need a good PI machine
for the Gold-fields here in OZ ..
AFter looking at PETER,s [WOODY-POO's] videos realized ,
I there for should have bought a used SD2000 ,Sd 2200 [Hindsite-Bugga] anyway I found a few more dollars & managed to Buy a F1A4 & changed the coil socket,ear ph socket ,Altered the bottom of the stalk [Cut of the plastic adapter & fitted a section of an old fisher adapter ,by trimming the fibre-glass F1a4 stalk & slid 2'' of the fisher stalk into the modified F1A4 stalk & used resin to fix it in] this allows the use of any M/lab coil ..
My next project is to build a Mono coil for it,I have the wire coming ,any info ,or hints -help would be appreciated !!

I would like to improve the F1A4 ,but at present cannot afford to have the mods done,maybe later down the track ??

OK thats ME a NEWBIE to this hobby I live 200ks Nth of Adelaide [Midnorth] about 8 hours from the Vic gold fields ,Hoping to take our old converted coaster,for a few weeks to try out the detectors in a few weeks..

I added  a couple pics ,,My untidy work bench where I do some tinkering..this is in my outside shed & its too cold to work there these frosty nights ,HA,Haar..

MY crude coil winding set-up.where I made some Coils for my H/built VLF IDX ..
I built a Coplaner type $ several DD types

CHEERS TO ALL BARRY..